The present invention relates generally to printing presses, and more particularly, is directed to a printing roller having a printing sleeve mounted thereon, and a method for mounting and dismounting printing sleeves from the printing roller.
In the printing press art, printing sleeves are fit onto rigid, incompressible printing cylinders. The sleeves are relatively expensive to manufacture.
U.S. Pat. No. 4,903,597 to Honge et al discloses a method of mounting a sleeve on a printing cylinder by supplying pressurized air between the printing cylinder and the sleeve in order to enable the sleeve to slide onto the printing cylinder. As with conventional printing cylinders, the printing cylinder of Honge et al is made of a rigid material that is not compressible. However, the sleeve is made of an elastic or resilient material, and specifically, a polymeric laminate material which has a constant thickness and cross-sectional diameter. Initially, a portion of the sleeve is force fit onto the cylinder, and thereafter, pressurized air is supplied through the interior of the cylinder and then through radial oriented holes in the cylinder. As a result, the sleeve expands by the force of the air pressure, providing a cushion of air between the sleeve and the rigid printing cylinder. This permits the sleeve to easily slide over the printing cylinder. However, as with conventional methods, the sleeve is relatively expensive. Related inventions which disclose expanding the outer sleeve by means of air pressure are disclosed in U.S. Pat. No. 5,324,248 to Quigley and U.S. Pat. No. 5,497,549 to Rademacher. However, again, specialized and expensive sleeves must be used.
U.S. Pat. No. 4,378,622 to Pinkston et al discloses a method of making a compressible printing roller. The roller includes a rigid shaft having a microporous inner layer made of a rubber material thereon. The inner layer is made of a cured and leached rubber material with interconnected cavities defined therein such that the voids represent between 30% to 70% of the total volume of the microporous inner layer. A thin tubular outer layer made of any suitable polymeric material which is non-porous and of solid cross-section throughout and free of voids, is mounted on the inner layer. In order to do so, the inner layer is compressed, whereupon the tubular outer layer is inserted thereover. Then, the inner layer is released, whereupon it expands and grabs the outer layer. The means for compressing the inner layer is a metal sleeve tool placed around the tubular inner layer, which is removed after the tubular outer layer is placed over the inner layer. It is clear from this patent that the outer layer is not intended to be easily replaced once the outer layer is inserted over the inner layer. Further, because of the porous nature of the inner layer, pressurized air could not be used for compressing the same.
Other patents are interest are U.S. Pat. Nos. 4,178,664; 4,391,898; 5,216,954; 5,256,459; 5,351,616; 5,352,507; 5,415,612; 5,520,600; 5,544,584; and 5,577,443.
Accordingly, it is an object of the present invention to provide a printing roller having a printing sleeve mounted thereon, and a method for mounting and dismounting sleeves from the printing roller, that overcomes the problems with the aforementioned prior art.
It is another object of the present invention to provide a non-expandable printing sleeve mounted on a compressible printing roller.
It is still another object of the present invention to mount the sleeve on the printing roller by providing pressurized air between the sleeve and printing roller in order to compress a covering layer of the printing roller.
It is yet another object of the present invention to provide a printing roller having a sleeve mounted thereon, and a method for mounting and dismounting sleeves from the printing roller that is easy and economical to use and manufacture.
In accordance with an aspect of the present invention, a roller system includes a cylindrical member; a covering layer fixedly mounted on the mandrel, the covering layer being resilient and compressible; a sleeve made of a non-expandable material and removably mounted on the covering layer; and an arrangement for supplying a pressurized gas between the covering layer and the sleeve in order to compress the covering layer and permit mounting of the sleeve on the covering layer and dismounting of the sleeve from the covering layer.
Preferably, the cylindrical member is comprised of a cylindrical mandrel with a cylindrical surface having at least one bore extending therethrough; the covering layer includes at least one opening in fluid communication with the at least one bore; and the arrangement for supplying a pressurized gas includes a supply of pressurized gas connected with the at least one bore for supplying the pressurized gas through the at least one bore and out through the at least one opening to a position between at least a portion of the sleeve and the covering layer.
The at least one bore is located close to one end of the mandrel. In one embodiment, the at least one opening is formed by a substantially annular cut-away groove in the covering layer. In another embodiment, the at least one opening includes a plurality of interconnected openings in the covering layer. Further, the at least one opening is provided at an angle relative to a direction perpendicular to an axial direction of the mandrel, with the angle being in a range of approximately 30xc2x0 to 45xc2x0.
There is further a device connected with the cylindrical member for rotatably holding the cylindrical member.
The covering layer is made of a material selected from the group consisting of rubber, urethane and polymers. The material can be a a closed cell foam material or an open cell foam material with a non-porous layer thereover. The sleeve is made of a metal material or a plastic material.
In accordance with another aspect of the present invention, a method of mounting a non-compressible sleeve on a resilient and compressible covering layer of a roller and dismounting the sleeve from the covering layer of the roller, includes the steps of supplying a pressurized gas to a position between at least a portion of the sleeve and the covering layer; compressing the resilient and compressible covering layer with the pressurized gas to an outer diameter slightly smaller than an inner diameter of the sleeve; axially moving the sleeve over the compressed covering layer when mounting the sleeve on the covering layer; stopping the supply of the pressurized gas from the position between at least a portion of the sleeve and the covering layer such that the covering layer expands to form an interference fit between the sleeve and the covering layer; and axially moving the sleeve from the compressed covering layer when removing the sleeve from the covering layer after the covering layer has been compressed.
The step of supplying pressurized gas to the position between at least a portion of the sleeve and the covering layer, includes the step of supplying the pressurized gas from an interior of the covering layer through at least one opening to a position between at least a portion of the sleeve and the covering layer in order to compress the covering layer and permit mounting of the sleeve on the covering layer and dismounting of the sleeve from the covering layer.
Preferably, the covering layer is mounted on a mandrel having at least one bore therein in fluid communication with the at least one opening in the covering layer; and the step of supplying pressurized gas to the position between at least a portion of the sleeve and the covering layer, includes the step of supplying the pressurized gas from an interior of the mandrel through the at least one bore and the at least one opening to a position between at least a portion of the sleeve and the covering layer in order to compress the covering layer and permit mounting of the sleeve on the covering layer and dismounting of the sleeve from the covering layer.
In another embodiment, the step of supplying pressurized gas to the position between at least a portion of the sleeve and the covering layer, includes the step of supplying the pressurized gas through an end of the mandrel to the interior of the mandrel from a supply of pressurized gas.
The above and other objects, features and advantages of the invention will become readily apparent from the following detailed description thereof which is to be read in connection with the accompanying drawings.